I think the only way she could possibly sells things sold at Chantilly (rather expensive show) for a profit that quick was that she was selling them to criminals.

By the time you pay the going price and taxes it will be a rare event where you can sell it to another legal buyer for a profit. He/she could go buy it for the same price and not your mark up, if they can legally buy it.

Not sure selling them quickly is a crime, but selling them to banned people is.